Abstract

The echolocation signals of a false killer whale (Pseudorca crassidens) were collected during a wall thickness discrimination task and compared to clicks recorded during an identical experiment in 1992. During the sixteen year time period, the subject demonstrated a loss of high frequency hearing of about 70 kHz. Clicks between the two experiments were compared to investigate the effect of hearing loss on echolocation signals. There was a significant reduction in the peak frequency, center frequency and source level of clicks between the two time periods. Additionally, the subject currently produces more signals with low frequency peaks and fewer signals with high frequency peaks than she did in 1992. These results indicate the subject changed its echolocation signals to match its range of best hearing.

Received 10 July 2010Accepted 21 July 2010Published online 18 October 2010

Acknowledgments:

The authors would like to thank Stuart Ibsen for the development of the hydrophone array and subsequent experimental advice, Whitlow Au, Alexander Supin, Marc Lammers, and Brian Branstetter for their knowledge and advice, Stephanie Vlachos, Dera Look, and Vincent De Paolo for their hard work and dedication, and everyone at the Marine Mammal Research program and the Hawaii Institute of Marine Biology at the University of Hawaii. This research was supported by the Office of Naval Research Grant No. N00014-08-1-1160 to Paul Nachtigall for which the authors would like to thank Neil Abercrombie. This work was conducted under U.S. Marine Mammal Permit No. 978-1567 issued to Paul E. Nachtigall by the U.S. National Marine Fisheries Service Office of Protected Resources. This is Hawaii Institute of Marine Biology Contribution No. 1398.